This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A188115 #9 Jul 22 2025 10:59:45 %S A188115 0,2,2,8,16,52,152,484,1536,5064,16946,57528,197616,686588,2407538, %T A188115 8510428,30300268,108575996,391301260,1417520988,5159160792, %U A188115 18857230104,69193592020,254802169904,941383915572,3488574124056,12964318919492 %N A188115 Number of strictly increasing arrangements of n nonzero numbers in -n..n with sum zero. %C A188115 Column 2 of A188122 %H A188115 R. H. Hardin, <a href="/A188115/b188115.txt">Table of n, a(n) for n = 1..31</a> %e A188115 Some solutions for n=6 %e A188115 .-5...-5...-6...-6...-5...-6...-6...-6...-6...-5...-6...-4...-6...-6...-5...-6 %e A188115 .-4...-4...-4...-5...-4...-5...-5...-3...-4...-3...-5...-3...-4...-2...-4...-4 %e A188115 .-1...-1...-2...-1...-2...-4...-3...-2...-1...-1...-1...-1...-2...-1...-2...-1 %e A188115 ..1....1....2....3....2....4....3....2....2....2....2....1....3....1....1....2 %e A188115 ..4....3....4....4....4....5....5....3....3....3....4....2....4....2....4....4 %e A188115 ..5....6....6....5....5....6....6....6....6....4....6....5....5....6....6....5 %K A188115 nonn %O A188115 1,2 %A A188115 _R. H. Hardin_ Mar 21 2011